<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        #canvas {
            border: 1px solid black;
        }
    </style>
</head>
<body>
<canvas width="600px" height="500px" id="canvas"></canvas>
<script>
    const ctx = document.querySelector("#canvas").getContext("2d")

    // 椭圆  x,y,radiusX,radiusY,rotation,startAngle,endAngle,bool

    // 竖向 ctx.ellipse(300, 200, 150, 100, 90 * Math.PI / 180, 0, 360 * Math.PI / 180)
    ctx.ellipse(300, 200, 200, 100, 0, 0, 360 * Math.PI / 180)
    ctx.stroke()

</script>
</body>
</html>